I agree I realized the row is usually mixed of numbers and texts.
On Apr 12, 2011, at 4:14 AM, Romain Francois wrote:
> Le 12/04/11 10:57, deqiang sun a écrit :
>> Hi Dirk,
>>
>> Thanks very much for your example. From this example I learned how to
>> passing data back and forth between R and C++.
>> The example is R code and uses piece of C++ code in side R program.
>> Well, it's better if you put this example(by only making slight changes to
>> make R embeded in C++) inside package RInside.
>>
>> Accessing data by column name is the feature I ( and other people) usually
>> want.
>> However, is there a way to access the data Frame by row number?
>
> No. You access the column, and then do whatever with each element, as in
> Dirk's example.
>
>> Regards.
>>
>> Dsun
>> On Apr 8, 2011, at 9:56 AM, Dirk Eddelbuettel wrote:
>>
>>>
>>> Ok, I now committed a slightly nice example to RcppExamples, a package I
>>> should revamp to contain more examples. In there, we now receive a
>>> data.frame, operate on each column, create a new data and return old and
>>> new.
>>>
>>> The core of the code (inside the try/catch protection) is
>>>
>>> // construct the data.frame object
>>> Rcpp::DataFrame DF = Rcpp::DataFrame(Dsexp);
>>>
>>> // and access each column by name
>>> Rcpp::IntegerVector a = DF["a"];
>>> Rcpp::CharacterVector b = DF["b"];
>>> Rcpp::DateVector c = DF["c"];
>>>
>>> // do something
>>> a[2] = 42;
>>> b[1] = "foo";
>>> c[0] = c[0] + 7; // move up a week
>>>
>>> // create a new data frame
>>> Rcpp::DataFrame NDF =
>>> Rcpp::DataFrame::create(Rcpp::Named("a")=a,
>>> Rcpp::Named("b")=b,
>>> Rcpp::Named("c")=c);
>>>
>>> // and return old and new in list
>>> return(Rcpp::List::create(Rcpp::Named("origDataFrame")=DF,
>>> Rcpp::Named("newDataFrame")=NDF));
>>>
>>>
>>> Dirk
>>> --
>>> Dirk Eddelbuettel | e...@debian.org | http://dirk.eddelbuettel.com
>
> --
> Romain Francois
> Professional R Enthusiast
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> http://romain-francois.com
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